1. Field of the Invention
The present invention is generally concerned with clutch release bearings of the type designed to be fitted to automotive vehicles, for example, and it is more particularly directed to the case in which, in order to disengage a clutch, the clutch release bearing must operate in traction on the clutch release device which the clutch comprises for this purpose.
2. Description of the Prior Art
As is known, a clutch release bearing of this kind generally comprises a maneuvering member through the intermediary of which it is adapted to be operated on by a control member, in practice a clutch release yoke, and a drive member which is axially coupled to said maneuvering member and through the intermediary of which it is adapted to operate on the clutch release device of the clutch to be actuated, said maneuvering member comprising, for the control member to act on, two radial arms which, extending axially towards the drive member at a distance therefrom, occupy respective diametrically opposite positions relative to one another on respective opposite sides of a diametral plane of the assembly, hereinafter referred to for convenience as the engagement plane.
In practice, there is usually orthogonally associated with each of these radial arms an axial guide surface for guiding the control member and preventing the clutch release bearing rotating on the latter, parallel to the engagement plane and perpendicular to the diametral plane of the assembly passing through median parts of the radial arms, hereinafter referred to for convenience as the traction plane.
At present, the axial guide surfaces which the maneuvering member thus features, which are usually separated by a distance only very slightly smaller than that between the fingers of the clutch release yoke which in practice constitutes the control member of the clutch release bearing concerned, extend substantially equally on either side of the traction plane of the latter, like the radial arms with which they are associated.
This arrangement has given and can continue to give satisfaction.
However, problems arise in the use of clutch release bearings of this type.
Difficulties arise on fitting the assembly, that is to say during the necessary axial movement towards one another of, on the other hand, the engine block which carries the clutch and thus, through the intermediary of the latter, the clutch release bearing and, on the other hand, the gearbox on the housing of which the clutch release yoke is pivotally mounted.
It is then necessary to engage the clutch release yoke on the maneuvering member of the clutch release bearing, between the radial arms of the latter, which are in practice disposed at its end, and its main part.
It is therefore necessary to associate with the axial movement towards one another of the engine block and the gearbox a pivoting movement for the clutch release yoke enabling it, initially offered up flat, parallel to the axis of the assembly so as to pass beyond the radial arms of the clutch release bearing, to become progressively hooked over the latter transversely to said axis.
As will be readily understood, if during this operation the clutch release bearing is not offered up to the clutch release yoke with the proper angular orientation relative to the axis of the assembly, the axial surfaces associated with its radial arms, by virtue of the distance between them, oppose the proper engagement of the clutch release yoke, the edges of the fingers of the latter then striking against these axial surfaces. It is then necesary to reverse the relative axial movement of the engine and the gearbox, and in practice this is after they have been fastened together, involving the removal of the retaining bolts.
To overcome this difficulty, it is proposed in UK Patent Application No. 2 071 255 to confer a polygonal transverse cross-section on the main part of the maneuvering member of the clutch release bearing.
Conjointly with this, however, the fingers of the clutch release yoke must be of different length so as to come in turn into contact with the aforementioned main part when the clutch release yoke is engaged on it, the first of these fingers which comes into contact with this main part rotating it around the axis of the assembly so as to confer on it the correct angular position relative to the second.
Given this rotation, the radial arms of the maneuvering member of the clutch release bearing on which the fingers of the clutch release yoke are adapted to operate must then be of relatively large extent in the circumferential direction and, in practice, they constitute non-separate parts of a common circumferentially continuous radial flange, which is prejudicial to the weight of the assembly. Moreover, an arrangement of this kind is suitable only for release bearings of which the overall dimensions, particularly in the axial direction, are sufficient for the longer arm not to encounter any obstacle, in particular on pivoting of the yoke after passing beyond the radial arms at the assembly stage.
A general objective of the present invention is an arrangement providing a very simple means of overcoming these difficulties, whilst also avoiding the disadvantages outlined hereinabove.